Di(4-5 carbon branched primary alkyl) dithiophosphate promoters for the flotation of copper middlings

ABSTRACT

In the flotation of copper sulfides; diisobutyl dithiophosphates, diisoamyl dithiophosphates and di(2-methyl-1butyl) dithiophosphates give a superior flotation rate, recovery and selectivity as compared with conventional dialkyl dithiophosphates, often permitting a coarser grind, and flotation of middlings, followed by a regrind ultimately resulting in a higher recovery of copper.

United States Patent 1 1 3,570,772

[72] Inventors Robert Ben Booth [50] Field of Search 209/166, Stamford,Conn.; 167, 3, 10; 241/20, 24, 29 Herman Hartjens, Ridgewood, N.J.; JohnJoseph Falvey, Noroton Heights, Conn. [56] References C'ted [21]Appl.No. 852,504 UNITED STATES PATENTS 1 Filed Aug-22,1969 2,664,19912/1953 Barkev 209/167 2] Patented 2 3 3,086,653 4/1963 Booth 209/166 [7Amgnee 33x33 ii f ompany Primary Examiner-Tim R. MilesContinuation-impart of application Ser. No. 617,069, Feb. 20, 1967, nowabandoned.

[54] DI(4-5 CARBON BRANCHED PRIMARY ALKYL) DITHIOPHOSPHATE PROMOTERS FORTHE FLOTATION OF COPPER MIDDLINGS Assistant Examiner-Robert HalperAttorneySamuel Branch Walker ABSTRACT: In the flotation of coppersulfides; diisobutyl dithiophosphates, diisoamyl dithiophosphates anddi(2- methyl-l-butyl) dithiophosphates give a superior flotation rate,recovery and selectivity as compared with conventional dialkyldithiophosphates, often permitting a coarser grind, and flotation ofmiddlings, followed by a regrind ultimately resulting in a higherrecovery of copper.

DI(4-5 CARBON BRANCHED PRIMARY ALKYL) DITHIOPHOSPHATE PROMOTERS FOR THEF LOTATION OF COPPER MIDDLINGS CROSS REFERENCES This application is acontinuation-in-part of our application Ser. No. 617,069, filed Feb. 20,1967, which is a continuationin-part of our application Ser. No.535,001, filed Mar. 17, 1966, both now abandoned in favor of thisapplication.

This invention relates to the beneficiation of sulfide ores for therecovery of copper values occurring therein; more particularly to aprocess of flotation in which a sulfide ore is floated in the presenceof a compound which in aqueous solution ionizes to give a dialkyldithiophosphate ion of the formula:

where R is a branched chain primary alkyl group of not more than 5carbon atoms. With less than 4 carbons, a primary alkyl group cannot bebranched. For purposes of convenience, these compounds are referred toas di(45 carbon branched primary alkyl) dithiophosphates. This includesthe diisobutyl dithiophosphates, the diisoamyl dithiophosphates and thedi( Z-methyl- 1 -butyl) dithiophosphates.

The promoter may be added as the free acid or as a salt such as theammonium or sodium or potassium or calcium salt. The material may beadded either in pure form as a solid or liquid, as the case may be, ormixed with excess alkalies such as sodium or potassium carbonates togive a dry powder; or as aqueous solutions.

Even when classed as a sulfide ore there may be some of the metal valuespresent as an oxide or an appreciable part of the metal may be presentas the oxide or in various oxidized fonns. The sulfide ores aregenerally beneficiated by crushing, and then grinding the ore to obtaina pulp; usually the grinding is wet grinding. A flotation promoter maybe added either after the grinding or in the wet grinding step.Frequently the promoter is added in the wet grinding step to aid inuniform distribution. A frothing agent or other additives may be addedand the ore is then aerated to produce a froth at the surface of thepulp, either by mechanical agitation while adding air, or by aerationalone. The metal values adhere to the bubbles in the froth and arefloated off from the surface of the aerated pulp. Such promoters aresometimes called collectors.

Such flotation operations are well known in the industry. U.S. Pat. No.1,593,232, F. T. Whitworth Art of Concentrating of Mineral Ores byFlotation, Jul. 20, 1926, describes the reaction product of phosphorouspentasulfide with cresylic acid as a promoter. U.S. Pat. No. 2,038,400,F. T. Whitworth, Flotation Reagent, Apr. 21, 1936, describes thereaction product of phosphorus pentasulfide with aliphatic alcohols.This patent shows the formula:

R-O S This patent does not refer to these compounds as diaryl or dialkyldithiophosphates but such are proper names for them.

Among such dithiophosphates which have been sold commercially are thediethyl, the diisopropyl, the di-sec-butyl, diliexyl and dicresyl. Thesematerials have been used alone and in combination and have been added asthe free acid, the sodium, potassium and ammonium salts.

Diisobutyl dithiophosphoric acid and its nickel salt are referred to inthe text Organo Phosphorus Compounds" Gennady M. Kosolapoff, John Wiley& Sons, Inc., New York, 1950 at page 253. A method of preparing isdisclosed on page 236 as a general method.

It has now been found surprisingly that the di(4--5 carbon branchedprimary alkyl) dithiophosphates as the sodium, potassium, ammonium andcalcium salts and including the dithiophosphoric acid itself, andmixtures thereof, are particularly useful as flotation promotersparticularly if the ore to be floated contains middling particles whichresult from coarse grinding or from intimate association of thecomponent minerals which make up the ore. The latter type of middlingsfrequently exist even after fine grinding.

Middling particles thus are composed of two or more, and often several,mineral species. Such polyphase particles are generally more difficultto concentrate by flotation than free mineral grains.

A. M. Gaudin, in the text, Flotation, McGraw Hill Book Company, Inc.,New York, 1957, in Chapter 13, pages 393 to 413, gives an excellentdescription of middling particles, and the problems and economicsinvolved in their treatment by flotation. While some ores arefree-milling ores, that is, the values are readily separated from thegangue by crushing and grinding to permit the application of flotationtechniques, other ores present a middling treatment problem which in thepast has been difficult to solve and in many cases has not been solvedadequately to date. The extractive metallurgist is forced to compromisebetween obtaining a desired high recovery of mineral values and thegrade of the concentrate produced. High recoveries in concentrates oflow grade entail high treatment costs in subsequent upgrading andrefining operations, which may force the rejection of larger percentagesof the containedmetal values so as to obtain a concentrate which issalable or amenable to further treatments. Also in many cases, themiddling particles are not recovered, even though amenable to standardrefining processes, and thus represent high losses of the desiredmineral values.

The di(45 carbon branched primary alkyl) dithiophosphate promotersdescribed in this invention provide a means of solving this middlingtreatment problem. The compounds can be given other names; for example,the diisobutyl compound is also named 0,0-diisobutylphosphorodithioate'. This nomenclature is currently used by ChemicalAbstracts and indexed under isobutyl.

Any theory of action is, of course, somewhat speculative and theapplicants do not wish to be bound by the correctness of such theory butobservations appear to be consistent with the theory that the di(45carbon branched primary alkyl) dithiophosphates have branched methylgroups on the ends of the alkyl chains, which improve the flotativeefficiency of the overall promoter molecule. The phosphorus-bearingpromoter, bonds to the surface of the ore particles and the alkyl groupsare in a better position to impart hydrophobicity to the ore particlesand to enhance their collection by the hubbles ofthe froth. Also thepossibility exists that the branching of the organic radicals in thestructure of the promoter enhances the interaction of the promoter onthe surface of the mineral surface and the frother molecule on thebubble surface, which serves to improve the collection of mineralparticles, particularly difficulty floatable middling particles.

Whether such theories are correct or speculative, it is found that acoarser grinding gives good recovery as if only a comparatively smallportion of the metal sulfides are exposed, still the present promotersare powerful enough to cause particles having such mineral value tofloat. Hence, a much coarser grind may be used, without loss of valuesto the rougher tailings, permitting a major reduction in the grindingcosts. Some ores are fairly readily ground; others are less amenabletoward grinding; so that fine grinding involves considerable power, timeand equipment and is costly. It is found that by using the present di(45carbon branched primary alkyl) dithiophosphates, larger particles havinga smaller proportion of sulfide ore value may be floated and as a resultrougher concentrate or first float is obtained containing a largerpercentage of the total mineral values than has been possible with priorart procedures.

The middlings, in this rougher concentrate, may be then reground andthus only a comparatively small portion of the total quantity of oremust be reground to separate the mineral values from the gangue. Asecondary, cleaner float may then be made in which the ore values areseparated from any gangue as the particles are then all fairly small,the valuable particles of ore have less gangue attached, and a highgrade of concentrate is obtained.

As the cost of grinding ores such as copper, lead, zinc, cobalt, nickel,molybdenum and cadmium, and mixtures thereof, is an appreciable andimportant part of the milling cost, the reduction in grindingrequirements without loss of grade or value in the final product is anadvantage. Usually it is found that there is less loss in the flotationtailings than with the more conventional promoters which have beenpreviously used. Even though the losses in the tailings are usually onlyof the order of 520 percent of the values in the ore, reduction in theselosses is extremely important. Large copper operations, for instance,may mine as much as 50,000 tons of ore a day. A small percentageincrease in recovery which may be accomplished without additional costsis of great economic value.

As set forth in the examples, certain prior art examples are used by wayof comparisons. The average major ore is treated by practices which arethe result of years of experimentation and practical experience. Theaverage mill is continually experimenting toward developing a flotationsystem or flow sheet which is more economical. In many mills anyimprovement which can be unequivocally identified by analysis isregarded as'a tremendous advantage. In most mills, improvements whichcan only be detected by statistical analysis are sufficient formanagement to switch from one promoter and/or flowsheet, to anotherpromoter and/or flowsheet. In a large mill, it is not uncommon to have afair size fraction of a mill, from percent for one-half, so designedthat it may be operated under somewhat varied condition so as to showcomparable operating costs on a major scale in plant operations. Theresults obtained by such comparisons are carefully studied, and in manyinstances an experimental period of running is necessary so thatanalytical errors can balance out and not conceal trace improvements.Thus, it can be seen that any change will show up by analysis as animprovement will immediately be incorporated in the mill flowsheet. Evenchanges which show such a slight improvement that comparison of resultson side-by-side operation on major scales for a month are needed to showthere is in fact an improvement are considered extremely important. Somemajor mills have pilot plants which can handle large daily tonnages orore, which are used primarily for checking on any possibility ofimprovement of flow sheets.

The form in which the present novel promoter is added is usually notcritical. It may be added as the free acid, a salt with sodium, calcium,ammonium, or as a mixture of the sodium salt with alkalies such assodium carbonate and potassium carbonate or as a solution in water. Theshipping convenience, and facility of handling and measuring isimportantly affected by the physical form, and the preferred form mayvary from mill to mill depending on transportation facilities andmetering and feeding equipment. The promoter is usually added after thegrinding operation, for maximum effectiveness, and thoroughly mixed withthe ore. As water is present, and the quantity of promoter is small, itis most unlikely that the ion that was originally associated with thepromoter has any effect on the system, and the acid and various saltforms give generally similar results.

In contrast, the nature of the alkyl group can have a critical effect onoptimum efficiency. As shown in the examples below, the di(45 carbonbranched primary alkyl) dithiophosphates have a much improved actionover conventional dithiophosphates.

Diisobutyl dithiophosphoric acid can be produced by the reaction ofdiisobutyl alcohol in the ratio of 4 moles to 1 mole of phosphoruspentasulfide by changing the alcohol to the reactor and adding thephosphorus pentasulfide in increments. Temperatures from a normal roomtemperature of about 20 C. up to about 50 C. give good and rapidreaction. At lower temperatures, the reaction becomes undesirably slow.At higher temperatures, the alcohol can volatilize, or by-products form.After the reaction is completed, unreacted phosphorus pentasulfide andsolid impurities may be filtered from the liquid obtained, which isdiisobutyl dithiophosphoric acid. Even with commercial grades of alcoholand phosphorus pentasulfide an excellent promoter is obtained. The freeacid is conveniently taken up in a hydrocarbon solvent such as heptaneor petroleum ether, and ammonia added to precipitate out the ammoniumsalt; or the free acid may be reacted with sodium carbonate and/orpotassium carbonate to form the sodium and potassium salts, or mixtures.Such reaction methods are conventional in the preparation of otheresters of dithiophosphoric acid.

The alcohols used as starting materials are:

CH3-OHCH2OH isobutyl alcohol isoamyl alcohol, also named3-methyl-1-butanol -methyl-1-butanol, also named active amyl alcohol,from its optically active carbon atom.

Mixtures of these alcohols may be used, so that the substituents on anyone phosphorus are not necessarily the same.

Another way to describe the alcohols is by the formula:

where m is l or 2, and n is l or 0, and the sum ofn and m is l or 2.

Mixtures of the promoters of the present invention are effective inattaining high recovery of metal values. Such mixtures may be preparedby blending dry promoters together and using the resulting mixture inflotation operations. Altemately mixed promoters may be prepared byknown methods by reacting mixtures of alcohols with phosphoruspentasulfide. The resulting reaction products are compounds in which thealkoxy groups attached to any one phosphorus may be the same ordifferent.

Manufacturing procedures which have been used with other alcohols may beconveniently used with the present alcohols, or mixtures thereof. As thedetails of such procedures are well known further description appearsunnecessary here.

Certain specific aspects of the present invention are set forth in moredetail in the following examples in which all parts are by weight unlessotherwise specified.

Operations are carried out at ambient temperatures in the mill which mayrange from slightly above freezing in the winter to temperatures of ahot summer day without deleterious effect on operating procedures. Thetemperature, where significant, is set forth in detail. All parts are byweight, unless otherwise stated.

EXAMPLE 1 A Norwegian copper ore (about 2.00 percent Cu) containingchalcopyrite and pyrite in a graphitic silicate gangue, was ground with5.0 lb./ton hydrated lime and conditioned for 2 minutes with 0.6 lb./tonyellow corn dextrine to control the flotation of graphite and 0.060lb./ton of a 6-8 carbon atom alcohol as frother. Sodium diisobutyldithiophosphate, 0.025 lb./ton, was added as copper promoter andagitated with the ore pulp for 2 minutes. Flotation was conducted for 8minutes with two further additions of the diisobutyl dithiophosphatepromoter of 0.0125 lb./ton each. A copper concentrate was removed, whichcontained 21.42 percent Cu in 9.00 percent of the total weight of theflotation feed and represented a recovery of 96.69 percent of the totalcopper.

In a second flotation test, on this ore, the identical procedure wasfollowed except that sodium disecondarybutyl dithiophosphate was used ascopper promoter and the frother requirement was higher, 0.108 lb./ton.The copper recovery was 87.39 percent in a concentrate which assayed19.62 percent Cu and represented 8.44 percent of the total weight of theflotation feed.

The above metallurgical results demonstrate that the bamate and 0.04pounds per ton of sodium isopropyl xanthate.

This combination had been found to produce the highest copper recoveryon this particular ore after evaluation of all available commercialcollectors prior to development of the present diisobutyldithiophosphate and represents the highest skill of a competitive art.

Comparative results at two different grinding levels are as diisobutyldithiophosphate promoter of the present invention follows;

Concen- Grind, Calculated trate. Tailing, Percent percent feed,perpercent percent recovery 'Iest No.: +65M Collector cent Cu Cu C11 C1130/31 11.0 B 1. 1. 65 20.20 0.228 87.2 32/33, 11. 0 Diisobutyl dithiophosphate 1. 68 20. 01 0. 214 88.2 34/35- 24. 4 13" 1. 62 18. 52 0. 25085. 8 36/37 24. 4 Diisobutyl dithio phosphate 1. 64 16. 68 0.210 88. 4

1 As the ammonium salt.

was more effective than the disecondarybutyl dithiophosphate promoterand required less frother to achieve flotation of the copper. The latterpromoter is used currently in many com mercial copper flotationoperations.

EXAMPLE 2 The same ore as used in example 1 also was employed in twoadditional flotation tests. The procedure was identical to that used inexample 1 except that in the first test 0.050 1b./ton diisoamyldithiophosphate as promoter and 0.084 lb./ton alcohol frother were used.The copper recovery was 9655 percent in aconcentrate assaying 13.55percent Cu.

.In the second test, 0.05 lb./ton of mixed di-primary-amyldithiophosphate, as described in U.S. Pat. No. 3,068,653 was employed aspromoter. 1n the test, the frother requirement wasihigher, 0.096lb./ton. The copper recovery was 95.62 percent in a concentrate assaying16.78 percent Cu. Thus, the diisoamyl dithiophosphate promoter of thepresent invention was more effective than the mixed di-primary-amyldithiophosphate as described in the prior test. The high recovery andlow grade show the remarkable pulling power on middlings.

EXAMPLE 3 A Canadian copper ore (1.45 percent Cu) was ground to minus100 mesh in the presence of 1.6 lb./ton hydrated lime, 0.05 'lb./tonsodium cyanide, and 0.1 lb./ton zinc sulfate. The ore pulp wasconditioned for 2 minutes with 0.06 lb./ton methylisobutyl carbinol asfrother and 0.02 lb./ton mixed sodium-potassium diisoamyldithiophosphate as promoter. Flotation was conducted for 4 minutes andresulted in the recovery of 93.9 percent of the copper in a concentrateassaying 20.44 percent Cu and representing 6.65 percent of the weight ofthe ore.

The tailings produced in the first two tests were screened and thefractions analyzed for copper. The results of these two analyses areshown below. It can be seen that in all size fractions above 150 mesh,the tailings produced with diisobutyl dithiophosphate had less copperthan with the standard collector B. As no free copper mineral was foundin the size fractions larger than 150 mesh, it is concluded that thelower tailings produced with ammonium diisobutyl dithiophosphate was dueto its superior ability to float middling particles of copper sulfidewhich contain both copper sulfide and gangue.

It is to be noted that the results were particularly spectacular on boththe 100 and the +65 mesh product. These particles had both copper valuesand gangue, which had not been broken apart by grinding operations.

EXAMPLE 5 This test on a second South American copper ore shows that theadditional recovery with diisobutyl dithiophosphate as the promoter ismaintained after the cleaner flotation without sacrificing grade offinal concentrate. The comparison was again between ammonium diisobutyldithiophosphate and the collector B of example 1. This collector is inregular use on the flotation of this ore.

Rougher Cleaner Calculated concenconeen- Percent recovery loud, trution,tration, Collector Percent Cu Percent Cu Percent Cu Rougher CleanerDiisobutyl dithiophosphate 1 1. 77 26. 41 52. 42 88.7 87. 4 B 1. S3 24.45 47.07 87. 1 86. 2

I A; the ammonium salt.

The collector dosage was the same as in example 4. The frother was pineoil at 0.05 pounds per ton. The alkalinity was at pH 1 l maintained withlime. This test is indicative of results on a fully integrated pilotplant operated at 1,000 pounds per hour of copper ore. At thisparticular plant when calculated for full operation, the additionalcopper recovery has a value of about $3,000 per day.

It is aiso to be noted that the cleaner concentrate has a higher gradewhich reduces smelting problems.

EXAMPLE 6 Two other copper ores, designated Ore No. 1 and Ore No. 2,were chosen. These ores assayed 1.37 percent copper and 1.56 percent Curespectively. Comparative tests were carried out with severalcollectors. The grind was 28 mesh with 19 percent +65 mesh; alkalinitywas adjusted to pH 10.5 with lime; promoter dosage was 0.05 pounds perton. The frother with the No. l ore was 0.05 pounds per ton of apolyglycol and for the No. 2 ore pine oil at 0.08 pounds per ton.Flotation times were respectively 5 and 7 minutes. For each ore allvariables other than the promoter were maintained constant. The averageof closely similar results from tests conducted in duplicate were asfollows:

Copper Copper Ore No. 1 Ore No. 2

rougher rougher tailing. tailing,

Promoter percent Cu percent Cu lsobutyl DTP 1 0. 238 0. 380 Secondaryhutyl DTP 1 0. 256 0. 435 n-Butyl DTP 1 0. 256 0. 438

1 Dithiophosphate, as the ammonium salt.

The copper content of the rougher flotation tailings represents a lossin copper values and this is a critical factor in determining theefficiency of a promoter in the flotation process.

The figures look particularly impressive when calculated out as therecovery of additional copper on a large-scale operation-with noadditional operating or capital costs. The reduction in copper loss inthe above examples corresponds to 0.36 lb. and 1.1 lb. of copper per tonor ore treated, which at large operations treating million tons of oreor more per year correspond to an additional copper recovery of3,600,000 to 1 1,000,000 lbs. of copper per year. The value of thecollector or promoter is great in relation to its cost, which in view ofthe raw materials used in the manufacture of the dithiophosphates wouldbe nominal as compared with the market in value ofcopper recovered.

EXAMPLE 7 Samples of Ore No. 2, as described in example 6, are groundand floated by the method and with lime and frother as described inexample 6. As flotation promoter, diisobutyl dithiophosphates in theform of the free acid, the sodium, potassium, and mixed sodium potassiumsalts, the sodium salt with a large excess of soda ash, and the calciumsalt were used on separate representative portions of the ore. Theflotation tailings were assayed for copper and the results of the testswere analogous to those obtained with the ammonium salt in example 6 asindicated in the following summary.

Percent Cu in rougher Promoter: tailing Ammonium salt 1 0. 380 Sodiumsalt (technical grade) 0. 380 Potassium salt 0. 384 Mixedsodium-potassium salts 0. 385

Sodium salt with excess sodium carbonate 50% by weight Sodium saltprepared as a 40% aqueous solution 0. 387 Calcium salt prepared as 20%aqueous solution -r. 0. 390 Free acid 0. 385

1 From Example 6.

EXAMPLE 8 A lead-zinc ore containing zinc sulfide, partly finelydisseminated in iron sulfide and gangue with considerable middlingpresent even at a fine grind of 70 percent minus 200 mesh and 100percent through 65 mesh, is subjected to rougher flotation with theconventional collector for that ore, namely, isopropyl xanthate, at 0.31pounds per ton of ore and ammonium diisobutyl dithiophosphate at 0.07pounds per ton of ore, under otherwise identical conditions using a pineoil frother at 0.04 pounds per ton. The feed material was tailing from alead flotation step. Lime was added to adjust the pH to 10.2 and coppersulfate added for sphalerite activation at 2.0 pounds per ton. Betterrecoveries and higher grade concentrates were obtained due to the bettermiddling recovery and greater selectivity towards the iron sulfide. Testresults were as follows:

This table shows a spectacular drop in the percentage of zinc lost inthe rougher tailings. The corresponding improved recovery of zinc showsup in the recovery percentages, the grade is much improved. In such arecovery operation the iron is regarded as a contaminant. Theimprovement in the grade of the zinc product through the reduction ofthe iron content in the rougher concentrate is an advantage in the useof the diisopropyl dithiophosphate promoter.

Whereas in the above examples, the advantages are primarily set forthfrom the standpoint of an improved recovery of a purer copper underconditions which are otherwise the same, advantages of the presentflotation reagents can be in part utilized towards (l) a higher recoveryof copper or (2) towards copper recoveries of an improved grade in theconcentrate or (3) towards a higher flotation rate permitting thetreatment of larger tonnages in given mill equipment of ore with arecovery equivalent to that using conventional reagents or (4) a greaterselectivity towards iron sulfide to reduce smelter expenses or (5) adecrease in the cost of grinding; or in part all of these. ln commercialoperations, the flowsheet can be modified towards an increased output ofcopper by forcing the grinding and flotation units, and accepting alower grade and lower recovery, or the recovery of copper in quantity orgrade can be optimized. The factors involved vary from time to time evenin the same rnill depending on the economic position of the market asregards both price and demand for copper, and other variables. It willbe understood by those most skilled in the art that with the superiorpromoters here taught, the chief engineer will modify the flowsheet tooptimize production under the particular conditions controlling at thetime of operation.

The applicability of the novel promoters for zinc, coppernickei,copper-cobalt, and silver ores is similar. It would unduly extend thelength of this specification to give complete details of all of theconditions in all ores under which advantages are found.

Promoters other than the diisobutyl dithiophosphate are shown in thefollowing examples in which, to avoid unduly lengthening thedescription, comparative date is given in tabular form.

EXAMPLE 9 Copper recovery Chile Utah orc, ore,

percent percent Di(primary amyl) DTP 86. 6 85. 1 D i(2-rnethy1-1-butyl)87. 3 B5. 2 D1(3-methyl-1-buty1) 87. 9 185. 7

EXAMPLE For a particular Arizona ore a thionocarbamate promoter has beenstandard, being chosen by mill operators with years of experienceattempting to use the most economically advantageous promoter of whichthey were aware for the particular ore.

Whereas the increase from 78.7 to 84.3 or 85.3 percent of copperrecovered does not appear to be too large, when it is considered thatthe extra copper is recovered at no additional cost, effectively, andthat operations at a major mill can run in the neighborhood of 10million tons of ore a year, it can be seen that the economical value ofthis recovery would run into several millions of dollars worth of copperper year.

The results tabulated are:

CHALCOPYRIIE ORE FROM ARIZONA Similar runs were made on a chalcocite orefrom Chile e l h nm hefelle caelz ss- Concen- Recovery tration, Tailing,Chalcocite Ore from percent percent Cu M082 Chile, lb./ton Cu CuThionocarbamate, 0018+ Na-isopropyl xanthate,

percent lb./ton.

0.4 (Standard) 17. 04 0. 331 77. 58 0. 42 Diisoamyl DTP, 0.05 18. 86 0.316 77. 93 0. 42 Diisobutyl DTP, 0.05 15. 98 0. 305 79. 42 0. 43

Again the standard collector is the one which has been used at this millbased on years of experience and is to be taken as representative of thebest that those skilled in the art can achieve.

- EXAMPLE 12 A run was made on a South American copper ore with allother variables the same other than the promoters. The mill reportbeing:

Collector Diiso- Diiso- Isopropyl butyl amyl xanthate DTP DTP Curecovery:

After 1 min 54.0 64. 9 76. 4 After 3 min 79. 1 80. 6 86. 2 After 6 rnin87. 2 86. 3 89. 4 Cone, total, grade percent 21. 8 19. 8 19. 8

EXAMPLE 14 Di(2- Di- Di(isomethylamyl amyl) l-butyl) DTP DTP Percent Curecovery:

After 1 min" 70. 7 71. 2 70. 6 After 3 min 13. 6 14. 4 14. 4 After 7 min2. 3 2. 4 2. 3 Percent total recovery. 86. 6 88. 0 87. 3

The increase in rate of recovery and the increase in total recovery areimportant.

It is to be noted that the increase in recovery in effect is copperrecovered without additional cost.

As most flotation operations are conducted at a pH of between about 9and about 1 l and usually 10 or 1 l, the form in which the di(45 carbonbranched primary alkyl) dithiophosphate is added is relativelyimmaterial and even if the di(45 carbon branched primary alkyl)dithiophosphate is blended with fairly large quantities of alkalies orother carriers to aid in its handling characteristics, such alkalies arepresent in too small a quantity to have a significant effect on the pHof the operation. The di(45 carbon branched primary alkyl)dithiophosphate could be used in a flotation circuit which operates onthe acid side of neutral and still give effective flotation, but theabove results are given as representing Collectors ThionocarbamateDi(secplus ondary Diiso- Diisoisopropyl Amy butyl) butyl amyl xanthatexanthate DTP DTP DTP Cu percent recovery:

After 2 min 66. 9 53. 5 66. 7 69. 1 72. 5 After 4 min. 74. 2 70. 9 73. 775. 1 78. 0 After 7 min. 77. 6 77. 6 77. 3 77. 9 79. 4 Cu Grade TotaL17.0 16.1 19.0 18. 9 16.0 Fe recovery, lb./ton

After 2 min. 14. 2 7. 9 7. 9 8. 7 l1. 0 After 4 min t 15. 7 12. 2 9. 39. 9 12.0 After 7 min l6. 6 l4. 2 l0. 3 10. 7 l2. 3

No'rE.Pr0cedure:

Grind 19.5% plus mesh with lime to give pH=11.0 in flotation. Condition1 minute with 0.05 lb./ton collector. 1 float 2 minutes with 0.05lb./ton collector. 2 float 2 minutes with 0.05 lb./ton collector. 3float 3 minutes wlth 0.05 lb./to11 collector.

EXAMPLE l3 facts more closely in accordance with accepted practices inore processing. Using the conditions otherwise the same, a mill reporton a Obviously the flotation may be accomphshed in one or copper orefrom Canada is as follows: more stages, or separately for sands andshmes, in accordance Procedure:

Grind to 4 percent 65 mesh Condition 1 minute with 0.045 lb./t0n ofcollector and 0.048 lb./ton of alcohol frother at pH 8.5

with conventional practice for promoters. .The present promoter givesimproved results even if blended in part with conventional promoters.The quantities illustrated by example are representative of best resultswith particular ores. Im-

proved results can be obtained with these di(4-5 carbon branched primaryalkyl) dithiophosphate promoters over a range of about 0.01 to 0.3pounds per ton of ore, depending on ore grade, size of grind, andmilling conditions. The most advantageous results are most often around0.05 lb./ton of ore.

We claim:

1. A process of beneficiating copper ores by froth flotation of an orepulp, in which a significant part of the ore is present in the rougherflotation as middlings, with a particle size of larger than 150 mesh,with many of such larger particles consisting of more than one mineralspecies, at least one of which is gangue in the presence of a flotationpromoter to recover copper values in said ore, the improvement whereinthe promoter consists essentially of a dithiophosphate of the formulawhere each R is a branched chain primary alkyl group of not more than 5carbon atoms selected from the group consisting of isobutyl, isoamyl andZ-methyl-l-butyl, with the Rs not necessarily the same and Me is adissociating cation selected from the group consisting of hydrogen,sodium, ammonium, potassium and calcium.

2. The process of claim 1 in which from about 0.01 to about 0.3 pound ofdiisobutyl dithiophosphate per ton of ore is used as the promoter.

3. The process of claim 2 in which at least 10 percent of the ore in theinitial flotation is larger than 65 mesh, and the concentrate from theflotation step is reground, and subjected to an additional flotationstep.

4. The process of claim 1 in which from about 0.01 to about 0.3 pound ofdiisoamyl dithiophosphate per ton of ore is used as the promoter.

5. The process of claim 4 in which at least 10 percent of the ore in theinitial flotation is larger than 65 mesh, and the concentrate from theflotation step is reground, and subjected to an additional flotationstep.

6. The process of claim 1 in which from about 0.01 to about 0.3 pound ofdi(2-methyl-1-butyl) dithiophosphate is used as the promoter.

7. The process of claim 6 in which at least 10 percent of the ore in theinitial flotation is larger than 65 mesh, and the concentrate from theflotation step is reground, and subjected to an additional flotationstep.

Column Column Column Column Column Column Column (SEAL) Attest:

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 5, 570.772

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EDWARD M.FLETCHER,JR. Attesting Officer Dated March 16, 197

lnven fl Robert Ben Booth, Hermen Hartjens & John Joseph I It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

12 after "particularly" omit to 49 "or ore" should read of ore '75"changing" should read charging 52 "-methyl" should read 2-methyl 54"or" should read of 61 "date" should read data 55 "0.4" should read 0.04

Signed and sealed this 18th day of April 1972.

ROBERT GO'ITSCHALK Commissioner of Patents FORM no-1n5o (10-69)USCOMM-DC D0

2. The process of claim 1 in which from about 0.01 to about 0.3 pound ofdiisobutyl dithiophosphate per ton of ore is used as the promoter. 3.The process of claim 2 in which at least 10 percent of the ore in theinitial flotation is larger than 65 mesh, and the concentrate from theflotation step is reground, and subjected to an additional flotationstep.
 4. The process of claim 1 in which from about 0.01 to about 0.3pound of diisoamyl dithiophosphate per ton of ore is used as thepromoter.
 5. The process of claim 4 in which at least 10 percent of theore in the initial flotation is larger than 65 mesh, and the concentratefrom the flotation step is reground, and subjected to an additionalflotation step.
 6. The process of claim 1 in which from about 0.01 toabout 0.3 pound of di(2-methyl-1-butyl) dithiophosphate is used as thepromoter.
 7. The process of claim 6 in which at least 10 percent of theore in the initial flotation is larger than 65 mesh, and the concentratefrom the flotation step is reground, and subjected to an additionalflotation step.